After two years of college, Hailey had been to a lot of parties, but she'd never seen anything like this. The house was massive. The music, thunderous. And yet the one thing Hailey couldn't get over was how many people were there. A horde of humanity was drinking on the lawn, dancing in the driveway, laughing and shouting and running around like maniacs. Like ants on a watermelon, they seemed to swallow everything around them.

At the front door, a boy Hailey didn't recognize gave her and Tommy each a red Solo cup and then sent them on their way. As crowded as it had been outside, the inside of...